QUANTIFICATION OF DUST-FORCED HEATING OF THE LOWER TROPOSPHERE

Aerosols may affect climate through the absorption and scattering of s olar radiation and, in the case of Large dust particles, by interactin g with thermal radiation(1-3). But whether atmospheric temperature res ponds significantly to such forcing has not been determined; feedback mechanisms could increase or decrease the effects of the aerosol forci ng. Here we present an indirect measure of the tropospheric temperatur e response by explaining the 'errors' in the NASA/Goddard model/data-a ssimilation system. These errors, which provide information about phys ical processes missing from the predictive model, have monthly mean pa tterns that bear a striking similarity to observed patterns of dust ov er the eastern tropical North Atlantic Ocean. This similarity, togethe r with the high correlations between latitudinal location of inferred maximum atmospheric heating rates and that of the number of dusty days , suggests that dust aerosols are an important source of inaccuracies in numerical weather-prediction models in this region. For the average dust event, dust is estimated to heat the lower atmosphere (1.5-3.5 k m altitude) by similar to 0.2 K per day. At about 30 dusty days per ye ar, the presence of the dust leads to a regional heating rate of simil ar to 6 K per year.